The first two substantive chapters of the thesis estimate the effect of single sex secondary school education on educational achievement and labour market out- comes. The last chapter evaluates the impact of a tax credit aimed to encourage disabled people to work. The analysis is carried out using data from the UK and particular attention is paid to issues of endogeneity. Chapters 2 and 3 explore the association between single sex education and indi- viduals' achievement at school and in the labour market, respectively using data from the National Child Development Study (NCDS). The main findings from Chapter 2 suggest, after accounting for endogeneity, that single sex schooling increases the probability of continuing with education at the age of 16 by 14 percentage points (ppts). However, no effect was found for other educational outcomes. The analysis in Chapter 3 suggests the existence of a positive relationship with fulltime employment at the age of 33, and a positive effect on individuals' wages among those working fulltime at the age of 23. The quantile regression analysis suggested that the effect is mainly observed at the lower-middle part of the wage distribution. Finally, we found evidence that women from single sex schools are more likely to have a professional partner. In Chapter 4, using data from the UK Labour Force Survey, we evaluate the effectiveness of the Disabled Person's Tax Credit (DPTC). Using a difference in differences approach, we find an increase of 6.5 ppts in the employment rates of lone mothers with a disability and an increase of 5 ppts in the looking for a job probability of single men. This thesis contributes to the existing literature on the effects of single sex education by using a different identification strategy from other authors. It also provides evidence of the effectiveness of the DPTC, which has not been studied in a comprehensive way until now.